Video processing apparatus and mobile terminal apparatus

ABSTRACT

A video processing apparatus includes a detector which detects whether pattern portions such as wallpaper portions having a pattern or the like or no-picture area portions having a single color are contained besides contents in a video signal input thereto, and a corrector which corrects the video signal. If the pattern portions are contained in the input video signal, the corrector is controlled so as not to correct the video signal.

This application claims the benefit of priority of Japanese ApplicationNo. 2005-338000 filed Nov. 24, 2005, the disclosure of which also isentirely incorporated herein by reference.

TECHNICAL FIELD

The present invention relates to a video processing apparatus which issupplied with a video image and which can be viewed, and a mobileterminal apparatus.

BACKGROUND

An example of a multimedia computer system which converts an input RGBsignal to a luminance signal and a color-difference signal, extracts acharacteristic point in the luminance signal every frame, corrects theluminance signal and the color-difference signal, and conducts displayis disclosed in JP-A-2002-132225 (page 4 and FIG. 1).

Furthermore, it is disclosed in JP-A-2005-26814 to provide a side paneldetection circuit which detects a side panel and conduct picture qualityaccording to a result of the side panel detection and a result of videoluminance level detection.

SUMMARY

In application to a mobile terminal apparatus which operates with abattery, correcting the luminance signal and the color-difference signalevery frame increases power consumption. While one is out, anopportunity to charge the mobile terminal apparatus cannot be obtainedsometimes. If the power consumption increases, therefore, the use timebecomes short, resulting in poor convenience in use. Furthermore, ifsunlight is incident on a display device, it becomes hard to watchimages, resulting in a problem that the mobile terminal apparatus ishard to use outdoors or the like.

When converting contents having an aspect ratio of, for example, 4:3 toa video signal having an aspect ratio of 16:9 and corresponding to animage which is long sideways, for example, in a broadcasting station,wallpapers are added to the left and right of the contents sometimes. Ifsuch a video signal is subjected to picture quality correction, thenluminance and colors of the wallpaper portions are changed according tothe contents of the video signal and consequently there is a risk thatthe image becomes rather hard to watch and the convenience in user's usebecomes worse.

In addition, if black no-picture areas are added to the left and rightsides of the contents having the aspect ratio of 4:3, luminance andcolor information of the black no-picture areas are confused. Thisresults in a problem that average values of luminance and color of the4:3 contents themselves cannot be calculated accurately.

Therefore, an object of the present invention is to provide a videoprocessing apparatus and a mobile terminal apparatus improved inconvenience in use.

A video processing apparatus according to the present invention includesa detector which detects whether pattern portions such as wallpaperportions having a pattern or the like or no-picture area portions whichhave a single color are contained besides contents in a video signalinput thereto, and a corrector which corrects the video signal. If thepattern portions are contained in the input video signal, the correctoris controlled so as not to correct the video signal.

Other objects, features and advantages of the invention will becomeapparent from the following description of the embodiments of theinvention taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram showing a configuration example of a portabletelephone;

FIG. 2 is a block diagram showing a configuration example of a picturequality enhancement circuit;

FIG. 3 is a characteristic diagram showing a relation betweencolor-difference and saturation;

FIG. 4 is a block diagram showing a configuration example of acharacteristic point detector;

FIG. 5 is a flow diagram showing an example of detection processingconducted in a luminance characteristic point detector;

FIG. 6 is an example of a luminance histogram;

FIG. 7 is a flow diagram showing an example of detection processingconducted in a hue characteristic point detector;

FIG. 8 is an example of a hue histogram;

FIG. 9 is a flow diagram showing an example of detection processingconducted in a saturation characteristic point detector;

FIG. 10 is an example of a saturation histogram;

FIG. 11 is a flow diagram showing a configuration example of an I/Funit;

FIG. 12 is a flow diagram showing an example of detection processingconducted in a scene change detector;

FIG. 13 shows a processing flow example of luminance correctionconducted in a modulator;

FIGS. 14A and 14B show an example of a luminance histogram and anexample of correction characteristics, respectively;

FIGS. 15A and 15B show an example of a luminance histogram and anexample of correction characteristics, respectively;

FIGS. 16A and 16B show an example of a luminance histogram and anexample of correction characteristics, respectively;

FIG. 17 shows a processing flow example of hue correction conducted in amodulator;

FIG. 18 shows a processing flow example of saturation correctionconducted in a modulator;

FIG. 19 is a block diagram showing a configuration example of a portabletelephone;

FIG. 20 is a diagram showing an example of input-output characteristicof a photo sensor;

FIG. 21 shows an example of correction data;

FIG. 22 is a block diagram showing a configuration example of a picturequality enhancement circuit;

FIGS. 23A to 23D are diagrams showing characteristic examples of inputgradation versus output gradation in luminance signal;

FIGS. 24A and 24B are diagrams showing characteristic examples of inputgradation versus output gradation in luminance signal;

FIG. 25 is a block diagram showing a configuration example of backlightand a backlight drive circuit;

FIG. 26 is a diagram showing an example of LED current values;

FIG. 27 is a block diagram showing a configuration example of a picturequality enhancement circuit;

FIG. 28 is a block diagram showing a configuration example of a patternportion detection circuit;

FIG. 29 is a diagram showing positions of pattern portion detectionpoints in a display device;

FIGS. 30A to 30C show an example of internal waveforms of a patternportion detection circuit;

FIGS. 31A to 31C show an example of internal waveforms of a patternportion detection circuit;

FIGS. 32A to 32D show an example of internal waveforms of a patternportion detection circuit;

FIG. 33 is a flow diagram showing an example of processing conducted inan I/F circuit;

FIG. 34 is a flow diagram showing an example of processing conducted ina CPU;

FIGS. 35A to 35C show an example of an input video signal;

FIGS. 36A to 36C show an example of an input video signal;

FIG. 37 is a block diagram showing a configuration example of a picturequality enhancement circuit;

FIG. 38 is a block diagram showing a configuration example of acharacteristic area controller;

FIG. 39 shows an example of display positions of no-picture areas in aninput video signal;

FIGS. 40A to 40C show an example of internal waveforms of acharacteristic point detection area controller;

FIGS. 41A to 41C show an example of internal waveforms of acharacteristic point detection area controller;

FIGS. 42A to 42E show an example of internal waveforms of acharacteristic point detection area controller;

FIG. 43 is a flow diagram showing an example of processing conducted inan I/F circuit;

FIG. 44 is a flow diagram showing an example of processing conducted ina CPU;

FIGS. 45A to 45C show an example of an input video signal; and

FIG. 46 shows an example of correction characteristics.

DESCRIPTION OF THE EMBODIMENTS

The present invention can be applied to a video processing apparatus,such as a portable telephone, a PHS, a PDA, a notebook computer, amobile TV, and a mobile video recording apparatus and reproductionapparatus. In the ensuing description, however, the portable telephonewill be taken as an example.

First Embodiment

FIG. 1 is a block diagram showing a configuration example of a portabletelephone. A communication antenna 1 receives a radio wave transmittedthrough the air, converts the radio wave to a high frequency electricsignal, and inputs the high frequency electric signal to a radio circuit2. Furthermore, the antenna 1 converts a high frequency electric signaloutput from the radio circuit 2 to a radio wave, and emits the radiowave. On the basis of an order issued by a CPU (Central Processing Unit)7, the radio circuit 2 demodulates the high frequency electric signalreceived by the communication antenna 1, and inputs a resultant signalto a coding-decoding processing circuit 3. Furthermore, the radiocircuit 2 conducts modulation processing on an output signal of thecoding-decoding processing circuit 3 to convert it to a high frequencyelectric signal, and outputs the high frequency electric signal to thecommunication antenna 1. Under the control of the CPU 7, thecoding-decoding processing circuit 3 conducts decoding processing on theoutput signal of the radio circuit 2, outputs talking voice signal to areceiver 5, and outputs character and image data to the CPU 7.Furthermore, the coding-decoding processing circuit 3 conducts codingprocessing on voice input from a microphone 4 or character and imagedata edited by the user who operates keys 6. In the present embodiment,keys are used to as an operation unit used to input information or anorder. However, the operation unit is not restricted to keys, but avoice input unit or a touch panel input unit may be used.

The CPU 7 conducts general processing of the portable telephone. Forexample, the CPU 7 acquires a program from a memory 9 via a CPU bus 8,and waits for call incoming by controlling the coding-decodingprocessing circuit 3, the radio circuit 2, and the communication antenna1. Besides the program, fixed patterns recorded in the portabletelephone previously, a call incoming tone such as a melody, personalinformation such as a telephone directory or an address book, anddownloaded call incoming melody and image data are stored in the memory9. Upon call incoming, the CPU 7 reads out a caller's name, a callincoming melody, and a call incoming image, outputs voice data from aspeaker 11 via a DAC (Digital Analog Converter) 10, and displays imagedata on a display device 16 via a video I/F (Interface) 14 and a picturequality enhancement circuit 15 to notify a user of call incoming. And itbecomes possible for the user to conduct talking and conduct mailtransmission and reception by operating the keys 6.

A TV antenna 12 converts a received TV broadcast radio wave to a highfrequency electric signal and outputs the high frequency electric signalto a TV tuner 13. The TV tuner 13 conducts demodulation processing onthe input signal, thereby converts the input signal to an electricsignal of CMOS level, and outputs the electric signal to the CPU 7. TheCPU 7 initializes the TV tuner 13 and orders station selection. Inresponse to a request from the CPU 7, the tuner 13 periodicallytransmits information indicating the reception state such as a bit rateerror to the CPU 7.

The CPU 7 conducts video-audio separation processing on a signal inputfrom the TV tuner 13 and conducts video decoding processing and audiodecoding processing. The video image is displayed on the display device16 via the picture quality enhancement circuit 15. The voice isreproduced by the speaker 11 via the DAC 10. As a result, the user canview and listen to the TV broadcast. The received TV broadcast may beeither of analog broadcast and digital broadcast. In the presentembodiment, the CPU 7 includes an interface to which the output of theTV tuner 13 can be directly coupled. However, this is not restrictive,but a circuit for interface conversion may be used. The interfaceconversion circuit may be mounted on the CPU or may be mounted in astack form. If an image processing apparatus such as an applicationprocessor or a coprocessor is mounted on a portable telephone, then theinterface conversion circuit may be mounted on the same silicon chip asthe processor or may be mounted in a stack form of a different siliconchip. The interface conversion circuit may be mounted in a controller ora driver IC of the display device 16 and in the TV tuner 13. As for theconnection part between the interface conversion circuit and the CPU 7,dedicated terminals may be provided on the CPU 7 or the interfaceconversion circuit may be connected to the CPU bus 8.

A battery 20 is formed of a chargeable secondary battery such as alithium ion battery or a nickel hydrogen battery. The battery 20supplies power required for components included in the portabletelephone to operate. A power supply circuit 19 supplies voltages tocomponents in the portable telephone on the basis of power supplied fromthe battery 20. If the residual quantity of the battery becomes small,the battery 20 is charged by power supplied from a home outlet or a carbattery. In FIG. 1, illustration of connections between the componentsin the portable telephone and the power supply circuit 19 is omitted.

The picture quality enhancement circuit 15 conducts picture qualityenhancement processing on the video signal output from the CPU 7, andoutputs a resultant video signal to the display device 16. A backlight17 generates illumination light for the display device 16 on the basisof power supplied from a backlight drive circuit 18, and illuminates thedisplay device 16. For example, a cathode-ray tube, a white-colored LED,or three-color LEDs of red, green and blue are used as the light sourcefor the backlight 17. The backlight drive circuit 18 steps up or stepsdown the voltage supplied from the power supply circuit 19 or thebattery 20 in order to drive the backlight 17. The backlight drivecircuit 18 can adjust the brightness and color under the control of theCPU 7. The backlight drive circuit 18 may be formed independently asshown in FIG. 1, or may be formed as a part of the power supply circuit19. For example, if the power supply circuit 19 is formed as an LSI, thebacklight drive circuit 18 may be mixedly mounted on the same siliconchip or may be mounted in a stack form of a separate silicon chip.

A block diagram showing a configuration example of the picture qualityenhancement circuit 15 is shown in FIG. 2. An RGB-YUV converter 151converts the video signal of the RGB form to a luminance signal andcolor-difference signals, and outputs the luminance signal as Y and thecolor-difference signals as R-Y and B-Y.

The conversion of the video signal of the RGB form to the YUV signalscan be conducted according to the following equations.Y=0.290×R+0.5870×G+0.1140×B  (1)Cb=(−0.1687)×R+(−0.3313)×G+0.5000×B  (2)Cr=0.5000×R+(−0.4187)×G+(−0.0813)×B  (3)

A color difference-HS converter 153 conducts hue conversion andsaturation conversion on the color-difference signals R-Y and B-Y inputfrom the RGB-YUV converter 151, and outputs hue H and saturation S. Acharacteristic point detector 154 calculates characteristic data such asa minimum level, an average level, a maximum level and a histogram ofthe input video signal on the basis of the luminance signal Y input fromthe RGB-YUV converter 151 and the hue H and the saturation S input fromthe color difference-HS converter 153. The characteristic point detector154 writes the characteristic data into an I/F unit 155. The I/F unit155 issues an interrupt signal 141 to the CPU 7 at predetermined timing.Upon detecting the interrupt signal 141, the CPU 7 reads out thecharacteristic data stored in the I/F unit 155 via an internal bus 1551,determines correction data according to a predetermined algorithm, andwrites the correction data into the I/F unit 155 via the internal bus1551. A modulator 152 conducts modulation based on the correction datawritten into the I/F unit 155 by the CPU 7 on the input luminance signalY, hue H and saturation S, and outputs results as luminance Y′, hue H′and saturation S′. An HS-color-difference converter 156 converts theinput hue H′ and saturation S′ signals to color-difference signals(R-Y)′ and (B-Y)′ and outputs the color-difference signals (R-Y)′ and(B-Y)′. A YUV-RGB converter 157 converts the input luminance signal Y′and color-difference signals (R-Y)′ and (B-Y)′ to signals having the RGBform, and outputs resultant signals. The YUV-RGV conversion can beconducted according to the following equations.R=Y+1.402×V  (4)G=Y+(−0.34414)×U+(−0.71414)×V  (5)B=Y+1.772×U  (6)

A selector 158 selects either the output of the YUV-RGB converter 157 ora through signal 142 supplied from the video I/F 14, and outputs aselected signal to the display device 16. The selector 158 may becontrolled by the CPU. The selector 158 may be changed over when theresidual quantity of the battery has become equal to or less than acertain definite value. In the case of a portable telephone ofopen-close type, the selector 158 may be changed over in response to theopening and closing. If the selector 158 is changed over in response tothe opening and closing and the portable telephone has a folding shape,it is desirable to select the YUV-RGB converter 157 side when theportable telephone is opened. In the case of a shape which allowsviewing a display device in the closed state, as in a portable telephoneof two-axis hinge form having a second axis in a direction in which thedisplay device is rotated by 180° besides a rotation axis in a foldingdirection even if the portable telephone has a sliding, rotating orfolding shape, the YUV-RGB converter 157 side may be selected in theselector 158 when the portable telephone is closed. Furthermore, theselector 158 may be changed over according to contents to be displayed.For example, the YUV-RGB converter 157 side is selected in the selector158 when viewing TV, a still picture or a moving picture. The throughsignal 142 may be selected in the waiting state regardless of the shapeof the portable telephone or the opening-closing state. By the way, theterm “contents” means, for example, video information of a drama, amovie, a sport or the like.

By the way, in the case where text data such as a mail text or a captionis input, then processing such as the RGB-YUV conversion in the picturequality enhancement circuit 15 is not needed and consequently the CPU 7exercises control so as to select the through signal 142. In this case,operation of a portion surrounded by a dotted line 159 is stopped. As aresult, the power consumption can be reduced. Specifically, operationclock supply to the picture quality enhancement circuit 15 is stopped,or supply of power to blocks surrounded by the dotted line 159 isstopped. When stopping the supply of power, the output of the powersupply circuit 19 may be stopped, or the supply of power may be stoppedby providing a switch on the picture quality enhancement circuit 15 sideto cut off a power absorbing path.

Outline of operation conducted by the color difference-HS converter 153will now be described with reference to drawings. FIG. 3 is acharacteristic diagram showing relations between the hue (H) and thesaturation (S). The abscissa represents the level of the B-Y signal, andthe ordinate represents the level of the R-Y signal. A vector sum of theB-Y signal and the R-Y signal is a vector which represents the hue andthe saturation, and its angle represents the hue H and its magnituderepresents the saturation S. Therefore, the hue H can be found usingequation (7) and the saturation S can be found using equation (8).H=tan−1((R=Y)/(B−Y)  (7)S=SQR((R−Y)2+(B−Y)2)  (8)

As shown in FIG. 4, the characteristic point detector 154 includes, forexample, a luminance characteristic point detector 1541, a huecharacteristic point detector 1542 and a saturation characteristic pointdetector 1543. FIG. 5 is a flow diagram showing an example of detectionprocessing conducted by the luminance characteristic point detector1541. As shown in the flow diagram, the luminance characteristic pointdetector 1541 makes a level decision on the luminance signal Y inputthereto momentarily by taking a frame as the unit, and acquirescharacteristic data such as a maximum level, a minimum level, a levelfrequency of every area and an average level. With reference to FIG. 5,a detection processing example in the case where the input gradation ofthe luminance level is in the range of 0 to 255 and the input gradationis gradation areas of 16 stages will now be described. However, thedetection processing is not restricted to this. For example, 8 stages,32 stages or the like can be freely set in a range in which resourcessuch as a memory and a gate capacitance are provided. By the way, adetection processing program to be executed by the luminancecharacteristic point detector 1541 may be stored in the memory 9, or maybe stored in a memory provided in the luminance characteristic pointdetector 1541.

First, comparison is conducted to determine whether a luminance levelY(n) at an nth pixel is lower than a minimum level Ymin stored in thememory 9 (S501). As initial values of the minimum level Ymin and amaximum level Ymax, 255 and 0 are previously stored in the memory 9. Ifthe luminance level is lower than the current minimum level, theluminance level at the nth pixel is stored in the memory 9 as theminimum level (S502). If the luminance level is at least the minimumlevel, comparison is conducted to determine whether the luminance levelat the nth pixel is higher than the maximum level (S503). If theluminance level is higher than the maximum level, then the luminancelevel at the nth pixel is stored as the maximum level (S504). If theluminance level is equal to the maximum level or less, then a decisionis made whether the luminance level at the nth pixel is in the range of0 to 15 (S505). If the luminance level is in the range of 0 to 15, then1 is added to a value of Yhst0 (S506). Yhst0 indicates the number ofluminance levels included in the gradation area ranging from 0 to 15.

If the luminance level is not in the range of 0 to 15, then a decisionis made whether the luminance level is in the range of 16 to 31 (S507).If a result of the decision is yes, then 1 is added to a value of Yhst(S508). If the result of the decision is no, then a decision is madewhether the decision level is included in another gradation areasuccessively.

If the area determination of the luminance level is finished, then theluminance level at the nth pixel is added to the current total luminancelevel (S511). At S512, a decision is made whether processingcorresponding to one frame is completed. If a result of the decision isyes, an average luminance level is calculated by dividing the totalluminance level by the number n of pixels and the processing is finished(S514). If the result of the decision is no, then 1 is added to n (S513)and the processing returns to S501 and processing for the luminancelevel at the next pixel is conducted.

FIG. 6 shows an example of a luminance histogram. The abscissa indicatesareas of the luminance histogram, and the ordinate indicates thefrequency. By acquiring this histogram, characteristics of the luminancecan be grasped easily. For example, a decision can be made whether thepicture is a simply dark picture or a picture having a bright place suchas a moon or a star in a dark picture.

FIG. 7 is a flow diagram showing an example of detection processingconducted by the hue characteristic point detector 1542. As shown in theflow diagram, the hue characteristic point detector 1542 makes a leveldecision on the hue signal H input thereto momentarily by taking a frameas the unit, and acquires a maximum level, a minimum level, a levelfrequency of every area and an average level. With reference to FIG. 7,a detection processing example in the case where the hue level is in therange of 0 to 359 and the levels are divided into hue areas of 12 stageswill now be described. However, the detection processing is notrestricted to this. In the same way as the luminance characteristicpoint detection, a detection processing program to be executed may bestored in the memory 9, or may be stored in a memory provided in the huecharacteristic point detector 1542.

In the same way as the luminance level, detection is conducted at S701to S710 to determine which of hue areas Hhst0 to Hhst11 includes a huelevel H(n) at the nth pixel. If the area of the hue level is judged,then the hue level at the nth pixel is added to the current total huelevel (S711) and a decision is made whether processing corresponding toone frame is completed (S712). If the processing is completed (yes), theaverage hue level is calculated and the processing is finished (S714).If the result of the decision is no, then 1 is added to n (S713) and theprocessing returns to S701 and processing for the hue level at the nextpixel is conducted.

FIG. 8 shows an example of a hue histogram generated by using the areafrequency detected as described heretofore. The abscissa indicates areasof the hue histogram, and the ordinate indicates the frequency. Bygenerating this histogram, characteristics of the hue change can begrasped easily.

FIG. 9 is a flow diagram showing an example of detection processingconducted by the saturation characteristic point detector 1543. Thesaturation characteristic point detector 1543 makes a level decision onthe saturation signal S input thereto momentarily by taking a frame asthe unit, and acquires a maximum level, a minimum level, a levelfrequency of every area and an average level. With reference to FIG. 9,a detection processing example in the case where the saturation level isin the range of 0 to 99 and the levels are divided into areas of 12stages will now be described. However, the detection processing is notrestricted to this. In the same way as the luminance characteristicpoint detection, a detection processing program to be executed may bestored in the memory 9, or may be stored in a memory provided in thesaturation characteristic point detector 1543.

In the same way as the luminance level, detection is conducted at S901to S910 to determine which of saturation areas Shst0 to Shst19 includesa saturation level S(n) at the nth pixel. If the area of the saturationlevel is judged, then the saturation level at the nth pixel is added tothe current total saturation level (S911) and a decision is made whetherprocessing corresponding to one frame is completed (S912). If theprocessing is completed (yes), the average saturation level iscalculated and the processing is finished (S914). If the result of thedecision is no, then 1 is added to n (S913) and the processing returnsto S901 and processing for the saturation level at the next pixel isconducted.

FIG. 10 shows an example of a saturation histogram. The abscissaindicates areas of the saturation histogram, and the ordinate indicatesthe frequency. By acquiring this saturation histogram, the saturationchange of the input video signal can be detected.

FIG. 11 is a block diagram showing an example of an internalconfiguration of the I/F unit 155. The I/F unit 155 conducts signalwriting and reading between the CPU 7 and the picture qualityenhancement circuit 15 via an I/F register 1550. Upon being suppliedwith characteristic data such as the luminance level, hue and saturationfrom the characteristic point detector 154, a scene change detector 1552preserves these data. Upon being supplied with new data, the scenechange detector 1552 rewrites data and makes a decision whether there isa difference between the new data and old data. If there is adifference, the scene change detector 1552 judges that a scene changehas occurred, and issues an INT (interruption) 141 to the CPU 7. The CPU7 reads out new characteristic data from the I/F register 1550,generates new correction data, and updates correction data in the I/Fregister 1550. In the present example, the CPU 7 reads outcharacteristic data from the I/F register 1550. Alternatively, the I/Fregister 1550 may transmit data to the CPU 7. As for the scene change,for example, a change from a program to a CM (commercial message), achange from a daytime scene to a night time scene, a change of the imagepickup place, a changeover from a studio image to an on-the-spot image,and a changeover on a TV camera in a studio or a stadium can bementioned.

FIG. 12 is a flow diagram showing an example of detection processingconducted by the scene change detector 1552. At S1201, a differencebetween a new minimum luminance level and an old minimum luminance levelis found and new data is written into the I/F register 1550. As regardseach of a maximum luminance level, an average luminance level and thefrequency of every area as well, a difference is found in the same way.If the difference of the frequency in the area 15 is found (S1202), theprocessing proceeds to processing of the hue characteristic point. Asregards the hue as well, the difference of each of the minimum huelevel, the maximum hue level, the average hue level, and the frequencyis found in the same way as the luminance (S1203 and S1204). Thedifference at the saturation characteristic point is found (S1205 andS1206). A decision is made whether the difference in luminance, hue andsaturation at a characteristic point is “0”, i.e., the frame is the sameas the preceding frame (S1207). If there is no difference, update of thecorrection data is judged to be unnecessary and the processing isfinished. On the other hand, if the result of the decision is “no”, thenthe scene change detector 1552 judges that a scene change has occurred,outputs the interrupt request 141 to the CPU 7 (S1208), and finishes theprocessing.

The scene change detector 1552 operates as described above. If the frameis the same in pattern as the preceding frame, therefore, readout of thecharacteristic data, generation of correction data, and processing ofwriting into the I/F register 1550 can be omitted. As a result, it ispossible to reduce the processing load of the CPU 7 and reduce thecurrent consumption for data transfer.

An example in which differences of all of the luminance, hue andsaturation are detected is shown in FIG. 12. However, this is notrestrictive. Furthermore, it is not necessary to detect differences forall characteristic data such as the minimum level and the maximum level.For reducing the processing load in the CPU 7, it is most effective todetect a scene change on the basis of whether there is a difference inthe average level of the luminance signal which exerts great influenceupon the user's vision. Furthermore, for example, when both the minimumlevel and the maximum level of the luminance have changed, a decisionmay be made on the basis of a combination of characteristic data such asthe minimum level and the average level of hue. A scene change may bejudged to occur when the distribution area (abscissa) in the histogramhas changed.

In the example shown in FIG. 12, it is judged that there are no scenechanges when the difference in characteristic data is 0. Alternatively,it is possible to provide a definite threshold and judge that a scenechange has occurred when the threshold is exceeded. It is desirable toset the threshold individually for each of the characteristic data. Inorder to prevent the correction data from being updated according towhether there is a caption, a specific gradation area or frequency areamay be neglected. For example, it may be judged that a scene change hasnot occurred, even if the frequency in the histogram on the white sidehas changed. In addition to the case where a scene is detected by usingthe luminance level or the like, the scene change detector 1552 mayjudge that a scene change has occurred and output the INT 141 everydefinite time period or every definite number of frames.

The modulator 152 modulates the luminance, hue and saturation on thebasis of the correction data generated by the CPU 7. Hereafter, a methodof the modulation will be described.

FIG. 13 shows an example of a flow of processing conducted by themodulator 152 when modulating the luminance signal. First, a decision ismade whether the first gradation area (Yhst0) in the luminance histogramis 0 (S1301). If a result of the decision is no, blacklevel is set to 0(S1302). Here, the term “blacklevel” indicates a range of the inputgradation for which the output gradation is fixed to 0. The expression“blacklevel is set to 0” means that there is no range for which theoutput gradation is set to 0. If the result of the decision is yes, adecision is made whether the second gradation area (Yhst1) in theluminance histogram is 0 (S1303). If a result of the decision is no, theblacklevel is set to 0 to 15 (S1304). If the result of the decision isyes, a decision is made whether the third gradation area (Yhst2) in theluminance histogram is 0 (S1305). If a result of the decision is no, theblacklevel is set to 0 to 31 (S1306). If the result of the decision isyes, a decision as to proceeding to the fourth gradation area (Yhst3) isnot made and the blacklevel is set to 0 to 47 (S1307). By thus providinga limit value, it is possible to prevent the luminance from beingcorrected excessively.

Subsequently, a decision is made whether the sixteenth gradation area(Yhst15) in the luminance histogram is 0 (S1308). If a result of thedecision is no, whitelevel is set to 0 (S1309). Here, the term“whitelevel” indicates a range of the input gradation for which theoutput gradation is fixed to 255. The expression “whitelevel is set to255” means that there is no range for which the output gradation is setto 255. If a result of the decision is yes, a decision is made whetherthe fifteenth gradation area. (Yhst14) in the luminance histogram is 0(S1310). If a result of the decision is no, the whitelevel is set to 239to 255 (S1311). If the result of the decision is yes, a decision is madewhether the fourteenth gradation area (Yhst13) in the luminancehistogram is 0 (S1312). If a result of the decision is no, thewhitelevel is set to 223 to 255 (S1313). If the result of the decisionis yes, a decision as to the thirteenth gradation area (Yhst12) in theluminance histogram is not made and the whitelevel is set to 207 to 255(S1314). By thus providing a limit value on the white side, it ispossible to prevent excessive correction.

If the range for which the output gradation is fixed to 0 or 255 isdetermined, then expansion processing is conducted so as to usegradation ranging from 0 to 255 which can be output, with respect to theinput gradation except gradation portions (collapsed portions bysaturation) for which the gradation on the black side and the gradationon the white side are respectively fixed to 0 and 255 (S1315). As aresult, correction can be conducted so as to make the gradient (Ygain)of the output gradation relative to the input gradation large.

An example of modulation method of the luminance signal used in themodulator 152 will now be described with reference to FIGS. 14A to 16B.

FIG. 14A is a luminance histogram. In this example, a gradation range of0 to 47 (Yhst0 to Yhst2) on the black side is not present. In otherwords, this example corresponds to the case where a video signalcarrying a whitish image (the black level is floaty) in which black isscarce is input. Applying to the processing flow shown in FIG. 13, itfollows that blacklevel=0 to 47 and whitelevel=255. By conducting theexpansion processing, correction to the gradient Ygain=1.22 isperformed. The corrected relation of the output gradation to the inputgradation is referred to as corrected characteristics.

FIG. 14B shows a correction image using the correction characteristics.A dotted line 1401 indicates characteristics of the output gradationrelative to the input gradation in the case where the correction is notconducted. A solid line 1402 indicates correction characteristics. Sincethe output gradation is fixed to 0 in the range of 0 to 47 for which thegradation in the input video signal is not present, the gradient of theoutput gradation relative to the input gradation in the range of 47 to255 becomes great. As a result, it is possible to make the contrast ofthe output gradation relative to the input gradation large and displayan image which is easy to view.

FIGS. 15A-15B are diagrams showing a correction example in the casewhere a video signal having no gradation on the white side is input.FIG. 15A is a luminance histogram of the input video signal. FIG. 15Ashows an example in the case where a gradation range of 207 to 255(Yhst13 to Yhst15) on the white side is not present, i.e., a videosignal carrying a blackish video image is input. Applying to theprocessing flow shown in FIG. 13, it follows that blacklevel=0,whitelevel=207 to 255, and Ygain=1.22.

FIG. 15B shows an image of correction using the correctioncharacteristics. A dotted line 1501 indicates characteristics of theoutput gradation relative to the input gradation in the case where thecorrection is not conducted. A solid line 1502 indicates correctioncharacteristics. Since the output gradation is fixed to 255 in the rangeof 207 to 255 for which the gradation in the input video signal is notpresent, the gradient of the output gradation relative to the inputgradation in the range of 0 to 207 is made great and expansion isconducted as far as 0 which is the output dynamic range limit. By usingsuch correction characteristics, it is possible to make the contrast ofthe output gradation relative to the input gradation large and displayan image which is easy to view in the gradation on the black side.

FIGS. 16A-16B are diagrams showing a correction example in the casewhere a video signal having no gradation on the black side and the whiteside is input. FIG. 16A is a luminance histogram of the input videosignal. In this example, a gradation range of 0 to 31 (Yhst0 to Yhst1)on the black side and a gradation range of 223 to 255 (Yhst14 to Yhst15)on the white side are not present. Applying to the processing flow shownin FIG. 13, it follows that blacklevel=0 to 31, whitelevel=223 to 255,and Ygain=1.33.

FIG. 16B shows an image of correction using the correctioncharacteristics. A dotted line 1601 indicates characteristics of theoutput gradation relative to the input gradation in the case where thecorrection is not conducted. A solid line 1602 indicates correctioncharacteristics. Since the output gradation is fixed to 0 and 255respectively in the range of 0 to 31 and 223 to 255 for which thegradation in the input video signal is not present, the gradient of theoutput gradation relative to the input gradation in the range of 31 to223 is made great and expansion is conducted as far as 0 and 255 whichare the output dynamic range limits. By using such correctioncharacteristics, it is possible to make the contrast in the middlegradation large and display an image which is easy to view.

FIG. 17 shows a flow example of hue correction. In the presentembodiment, the user previously selects a color desired to be especiallyvivid and emphasized from among colors such as yellow, red, magenta,blue, cyan and green. And color correction is conducted on the basis ofthe color selected by the user and a peak area Hhst max in the huehistogram. FIG. 17 shows correction processing in the case where, forexample, blue is selected. First, a decision is made whether the peakHhst max in the hue histogram corresponds to Hhst8 which is an areapreceding an area Hhst9 corresponding to blue (S1701). If a result ofthe decision is yes, a hue adjustment value Hadj is set to 10 (S1702).If the result of the decision is no, a decision is made whether the peakarea Hhst max in the hue histogram corresponds to Hhst10 which islocated behind the area Hhst19 corresponding to blue (S1703). If aresult of the decision is yes, the hue adjustment value Hadj is set to−10 (S1704). If the result of the decision is no, then Hadj is set to 0and the processing is finished. As a result, the color set by the usercan be emphasized.

In the example shown in FIG. 17, correction is conducted on the basis ofthe color set previously by the user. However, this is not restrictive.For example, it is possible to detect a peak area in the hue histogramand correct colors in areas before and after the peak area to the colorof the peak area. In the case where a large quantity of components nearthe blue color are included as in a video image of the beach, therefore,it is possible to adjust the hue to the blue side and display a videoimage with blue emphasized.

FIG. 18 shows a flow example of saturation correction. A decision ismade whether the maximum level of the saturation is greater than 80(S1801). If a result of the decision is no, the saturation gain Sgain isset to 1.2 (S1802). If the result of the decision is yes, Sgain is setto 1.0 (S1803) and the processing is finished. When the maximumsaturation is equal to a certain determinate value or less, therefore,it is possible to emphasize the saturation gain and conduct display withmore vivid colors. Although in the example shown in FIG. 18 correctionis conducted when the maximum saturation is equal to a determinate valueor less, this is not restrictive. When the maximum saturation is equalto a determinate value or less, the gain may be lowered in order toavoid occurrence of color collapse due to saturation.

It is possible to view a favorable image having clear contrasts whileholding down the power consumption by detecting a scene change andconducting the signal modulation as heretofore described.

The time when the modulator 152 conducts modulation on the input videosignal may be immediately after an order is issued from the CPU 7 or maybe after a definite time or a definite number of frames have elapsed. Orthe modulation may be conducted transitionally so as to cause gradualconvergence to desired correction characteristics. If the CPU 7 judgesthe compression factor to be high on the basis of header information ofan image file before decoding or judges the receiving state to be pooron the basis of the bit error rate or the like acquired from the TVtuner 13, then the possibility of occurrence of block noise is high, andconsequently the degree of correction may be weakened to prevent theblock noise from being emphasized. On the contrary, if the CPU 7 judgesthe compression factor to be low, then the possibility of occurrence ofblock noise is low, and consequently the degree of correction may bestrengthened to conduct display with a higher picture quality. Forexample, if the compression rate is high, then the degree of correctionis weakened by changing the limit value of the blacklevel to 23,changing the hue adjustment value Hadj to 5, or changing the saturationgain Sgain to 1.1.

In the present embodiment, the example in the case where theabove-described picture quality enhancement processing is implemented bythe picture quality enhancement circuit 15 has been described. If theprocessing capability of the CPU 7 has a margin, however, a part or thewhole of the picture quality enhancement processing may be conducted ina software form in the CPU 7 without using the picture qualityenhancement circuit 15.

In the present embodiment, the example in the case where the scenechange detector 1552 is provided in the I/F unit 155 and the CPU 7conducts generation and update processing of correction data in responseto the INT 141 supplied from the scene change detector 1552 has beendescribed. Alternatively, the CPU 7 may conduct generation and updateprocessing when a specific picture such as an I picture or an IDR(Instantaneous Decoding Refresh) picture has been generated when anencoded image is decoded.

Second Embodiment

FIG. 19 is a block diagram showing another configuration example ofportable telephone. The same components as those shown in FIG. 1 aredenoted by like reference numerals, and description of them will beomitted. Since the portable telephone is used in various places such asindoors and outdoors, the illuminance in surroundings differs accordingto the use situation. In a bright environment such as outdoors in aclear day, light in surroundings is incident on the display device 16.This results in a problem that the gradation on the low luminance side,i.e., the black side of the displayed image becomes hard todiscriminate. The portable telephone shown in FIG. 19 includes a photosensor 21, and superposes correction data based on illuminance besidescorrection based on characteristic data of the input signal.

The photo sensor 21 includes a phototransistor and a photodiode. Anexample of output characteristics of the photo sensor 21 is shown inFIG. 20. The abscissa indicates environment illuminance, and theordinate indicates an output level of the photo sensor. As theenvironment illuminance increases, the output level of the photo sensor21 also becomes high. In the present example, the photo sensor 21 isprovided as means used to detect illuminance. Alternatively, theilluminance may be detected by using an output signal of a CMOS cameraor a CCD camera.

Correction data used to correct the output gradation when theilluminance detected by the photo sensor 21 has become at least apredetermined value are stored in the memory 9. FIG. 21 shows an exampleof correction data. A correction value is set every gradation area Yhst.In the present example, the output gradation on the black side iscorrected so as to make it easy to discriminate the gradation on theblack side. In the present example, one kind of correction data isprovided for the case where the illuminance is at least a predeterminedvalue. Alternatively, a plurality of kinds of correction data differingin correction values and gradation ranges to be corrected may beprovided. The correction data of the kinds may be stored in the memory9. Alternatively, for example, it is also possible to use the correctiondata shown in FIG. 21 as reference data and multiply the reference databy a coefficient depending upon the illuminance to calculate correctiondata.

FIG. 22 shows an internal block diagram of the picture qualityenhancement circuit 15. An RGB gain adjuster 1510 is added to thepicture quality enhancement circuit shown in FIG. 2. The same componentsas those shown in FIG. 2 are denoted by like reference numerals, anddescription of them will be omitted.

The illuminance detected by the illuminance sensor 7 is input to the CPU7. If the illuminance is at least a predetermined value, the CPU 7outputs a control signal to order the RGB gain adjuster 1510 to correctthe output gradation. Under the control of the CPU 7, the RGB gainadjuster 1510 reads out correction data from the memory 9 through theI/F unit 155 and adjusts the gain for the video signal. Hereafter,superposition operation of correction data based on illuminanceconducted by the RGB gain adjuster 1510 will be described with referenceto FIGS. 23A-23D.

FIG. 23A shows characteristics of the output gradation relative to theinput gradation of the luminance signal in the case where theblacklevel=0 to 47, whitelevel=255 and correction is not conducted bythe modulator 152. If the illuminance is at least a predetermined value,the output gradation relative to the input gradation is corrected asshown in FIG. 23B. Specifically, the RGB gain adjuster 1510 conductscorrection so as to emphasize the output gradation on the black side. Ina bright environment as well, therefore, an image which can be viewedeasily can be displayed. On the other hand, if the illuminance is lessthan a predetermined value, then the RGB gain adjuster 1510 does notconduct correction and the output gradation relative to the inputgradation remains that shown in FIG. 23A.

FIG. 23C shows a state in which the blacklevel=0 to 47, whitelevel=255and the modulator 152 has corrected the output gradation relative to theinput gradation in the range of 47 to 255. If the illuminance is atleast a predetermined value, the RGB gain adjuster 1510 corrects theoutput gradation relative to the input gradation by using correctiondata read out from the memory 9 as shown in FIG. 23D. In the presentexample, the RGB gain adjuster 1510 is controlled so as not to conductcorrection with respect to the range of blacklevel=0 to 47. If thecorrection quantity in the RGB gain adjuster 1510 is equal to adeterminate value or less, however, it matters little even if gainmodulation is conducted.

In the example heretofore described, the gradation on the black side isemphasized according to the illuminance. However, this is notrestrictive. Correction may be conducted according to the color of lightin the surroundings. For example, if the color of sunlight is reddish asin the evening sun, there is a problem that the color of the displayimage is made reddish under the influence of the sunlight.

In order to solve this problem, the photo sensor 21 includes threeindependent RGB (Red, Green and Blue) detection elements, and the CPU 7calculates ratios among those detection elements. As a result,modulation is conducted according to the color in addition to thestrength of sunlight.

The CPU 7 calculates ratios among RGB output colors of the photo sensor21. If any of the RGB components is large in quantity, the CPU 7controls the RGB gain adjuster 1510 to lower the correction value forthe color that is much in component. For example, if the CPU 7 detectsthat the light contains much R components as in the case where the lightin the surroundings is given by the evening sun or an incandescentelectric lamp, the CPU 7 orders the RGB gain adjuster 1510 to decreasethe correction data for R as compared with G and B.

FIG. 24A shows a state in which the output gradation relative to theinput gradation of the luminance signal is not corrected by themodulator 152, but it is corrected by the RGB gain adjuster 1510. FIG.24B shows a state in which the output gradation relative to the inputgradation in the range of 47 to 255 is corrected by the modulator 152,and correction is conducted by the RGB gain adjuster 1510. In each ofFIGS. 24A and 24B, correction is conducted to lower the gain for R ascompared with G and B. As a result, it is possible to keep ratios amongR, G, and B on the display device 16 at desired ratios and conductfavorable display. Here, the example of the case where the sunlightcontains much R component has been described. Also in the case where thesunlight contains much G or R component, however, correction can beconducted in the same way.

In addition to the modulation of the input signal, the color of thebacklight 17 may be modulated according to the color of light in thesurroundings.

FIG. 25 shows a configuration example of the backlight 17 and thebacklight drive circuit 18. Light source elements (LEDs) 171 to 173 arean R-LED, a G-LED and a B-LED, respectively. Current controllers 183 to185 individually control currents of the LED 171 to LED 173,respectively, on the basis of an order given by a control circuit 181. ADC-DC converter 182 steps up or steps down the voltage supplied from thebattery 20 to drive the LED 171 to LED 173. Based on the order given bythe CPU 7, the control circuit 181 sets current values of the currentcontrollers 183 to 185. In general, the luminosity of each of the LED171 to LED 173 is proportional to a current flowing between its anodeand cathode. Therefore, the luminosity can be individually controlledfrom the CPU 7 by controlling the currents flowing through the LED 171to LED 173 via the control circuit 181 and the current controllers 183to 185.

FIG. 26 shows an example of control exerted upon the LED 171 to LED 173when a large quantity of R component is contained in light in thesurroundings. The ordinate indicates currents let flow through the LED171 to LED 173. If a large quantity of R component is contained, thencontrol is exercised so as to reduce the current flowing through theR-LED 171 as compared with the LED 172 and the LED 173. By thusexercising control, it is possible to prevent the color of the displayimage from being changed by the color of light in the surroundings.

The example of the case where a large quantity of R component iscontained in the sunlight has been described. If a large quantity of Gis contained in the sunlight, however, then the current flowing throughthe green-colored LED 172 should be made less than the currents flowingthrough R and B. If a large quantity of B is contained in the sunlight,then the current flowing through the B-LED 173 should be made less thanthe currents flowing through R and G.

In the present example, the case where one R-LED 171, one G-LED 172 andone B-LED 173 are used as light source elements has been described.However, this is not restrictive. The present control method may beapplied to the case where a backlight of LED array type including aplurality of minute LEDs respectively corresponding to the colors or aself-luminous characteristic display such as an organicelectroluminescence (EL) display.

Heretofore, the example of the case where correction is conducted on thecolors of the sunlight by using the backlight 17 has been described. Ifthe sunlight illuminance is high, however, it is possible to view afavorable image by increasing the currents flowing through the LED 171to LED 173 at the same ratio. On the contrary, if the sunlightilluminance is low, it is possible to reduce the power dissipation byreducing the currents flowing through the LED 171 to LED 173 at the sameratio.

In the foregoing description, a portable terminal apparatus such as aportable telephone has been taken as an example. However, application ofthe present invention is not restricted to portable terminalapparatuses. The present invention may be applied to any apparatus aslong as the apparatus is a video processing apparatus by which a videoimage can be viewed. For example, the apparatus may be a terminalapparatus that does not have a communication function. Furthermore,since power consumption for the high picture quality display can be madelow, the present invention is effective especially for a portableterminal that operates with a battery. However, the present inventionmay be applied to a stationary terminal apparatus that operates withpower supplied from a home outlet.

Third Embodiment

When converting contents having an aspect ratio of, for example, 4:3 toa video signal having an aspect ratio of 16:9 and corresponding to animage which is long sideways, for example, in a broadcasting station,pattern portions such as patterned wallpaper areas or single-coloredno-picture area are added to the left and right of the contentssometimes. It is desirable that the pattern portions are stationary inorder to make the video image easy to see. However, a part of a mark orthe like may be changed.

If the video signal with the pattern portions added is subjected topicture quality correction by taking a frame as the unit or a scene asthe unit, there is a possibility that the video image will become ratherindecent because the luminance or color of the pattern portions changesaccording to the contents of the video signal. In the presentembodiment, an example of a portable telephone including a detector todetect whether there is a pattern portion and having a function ofstopping the picture quality correction when a pattern portion isdetected will be described.

FIG. 27 is a block diagram showing another configuration example of thepicture quality enhancement circuit in the portable telephone. A patternportion detector 1511 is added to the picture quality enhancementcircuit shown in FIG. 2 to detect pattern portions inserted on the leftand right of an image. The same components as those shown in FIG. 2 aredenoted by like reference numerals, and description of them will beomitted.

FIG. 28 shows a configuration example of the pattern portion detector1511. A horizontal position counter 15111 counts dot clock pulses in aninput video signal. When the count has reached a predetermined value,the horizontal position counter 15111 outputs a horizontal enablesignal. When the count has coincided with the number of pixels in thehorizontal direction of the display device 16, the horizontal positioncounter 15111 outputs a horizontal pulse and clears the count. Avertical position counter 15112 counts the horizontal pulses output fromthe horizontal position counter 15111. When the count has reached apredetermined value, the vertical position counter 15112 outputs avertical enable signal. When the count has coincided with the number ofpixels in the vertical direction of the display device 16, the verticalposition counter 15112 outputs a vertical pulse and clears the count.

An AND gate 15113 outputs a logical product of the horizontal enablesignal output from the horizontal position counter 15111 and thevertical enable signal output from the vertical position counter 15112.A latch circuit 15114 takes in and retains a value of the luminancesignal Y output from the RGB-YUV converter 151, on the basis of theoutput of the AND gate 15113.

FIG. 29 shows positions of pattern portion detection points on thedisplay device 16. As for the number of pixels on the display device 16,it is supposed that, for example, there are 320 dots in the horizontaldirection and 180 dots in the vertical direction. It is also supposedthat the aspect ratio is 16:9. An image obtained by inserting patternportions on the left and right of the contents having an aspect ratio of4:3 is displayed on the display device 16. If the number of dots of the4:3 contents in the vertical direction is set equal to 180 so as to makeit coincide with the number of pixels on the display device 16, then thenumber of pixels in the horizontal direction becomes 240 dots.Therefore, pattern portions each having 40 dots are displayed on theleft and right. Detection points are disposed in three places P11, P12and P13 in a pattern portion display area and three places P21, P22 andP23 in a contents display area. In other words, the detection points aredisposed in a total of six places.

Supposing that the top left position on the display device 16 is theorigin A having coordinates (x,y)=(0,0), coordinates of the detectionpoints are (20,20) for P11, (60,20) for P21, (20,90) for P12, (60,90)for P22, (20,160) for P13, and (60,160) for P23. In the presentembodiment, the pattern portions are inserted on the left and right of avideo image evenly and detection is conducted by using only the leftside. However, this is not restrictive, but detection may be conductedby using only the right side, or detection may be conducted by usingboth the left and right sides. If contents that is longer sideways than16:9 as in the CinemaScope size, there is a possibility that patternportions will be inserted above and below the contents display area andconsequently detection points may be disposed above and under the image.As for the number of detection points as well, it is sufficient thatthere is at least one detection point outside the contents display area.Or as many detection points as the number of pixels on the displaydevice 16 or the number of pixels in the contents may be provided as inthe frame memory.

An example of operation in the horizontal position counter 15111 willnow be described with reference to FIGS. 30A-30C. In the horizontalposition counter 15111, for example, 20 and 60 which are x coordinatesof the detection points and 320 which is the number of pixels in thehorizontal direction of the display device 16 are preset in order togenerate the horizontal enable signal. As for the presetting, it may beconducted from the CPU 7, or the preset values may be fixed within thehorizontal position counter 15111. The initial values are thus preset inthe horizontal position counter 15111. As a result, the horizontalposition counter 15111 counts dot clock pulses input thereto, andoutputs the horizontal enable signal which assumes a high level at thepreset 20th and 60th clock pulse. Furthermore, the horizontal positioncounter 15111 outputs the horizontal pulse which assumes a high level atthe 320th clock pulse. When the horizontal position counter 15111 hasoutput the horizontal pulse, it resets the count, resumes counting from“0”, and repeats the operation of periodically outputting the horizontalenable signal and the horizontal pulse at the above-described timing.

An example of operation in the vertical position counter 15112 will nowbe described with reference to FIGS. 31A-31C. In the vertical positioncounter 15112, for example, 20, 90 and 160 which are y coordinates ofthe detection points and 180 which is the number of pixels in thevertical direction of the display device 16 are preset in order togenerate the vertical enable signal. As for the presetting, it may beconducted from the CPU 7, or the preset values may be fixed within thevertical position counter 15112. The initial values are thus preset inthe vertical position counter 15112. As a result, the vertical positioncounter 15112 counts horizontal pulses output from the horizontalposition counter 15111, and outputs the vertical enable signal whichassumes a high level at the preset 20th, 90th and 160th count.Furthermore, the vertical position counter 15112 outputs the verticalpulse which assumes a high level at the 180th clock pulse. When thevertical position counter 15112 has output the vertical pulse, it resetsthe count, resumes counting from “0”, and repeats the operation ofperiodically outputting the vertical enable signal and the verticalpulse at the above-described timing.

An example of input and output waveforms of the AND gate 15113 is shownin FIGS. 32A-32D. FIGS. 32A-32D show an example of the case where thecount in the vertical position counter 15112 has reached 20. Only whenboth the horizontal enable signal and the vertical enable signal are atthe high level, the AND gate 15113 outputs the high level. Therefore,the output of the AND gate 15113 assumes the high level at the 20thclock pulse and the 60th clock pulse of the horizontal position counter15111 of the 20th count, 90th count and 160th count in the verticalposition counter 15112.

The latch circuit 15114 takes in the value of the luminance signal Y attiming of the AND gate 15113 assuming the high level, and maintains itover one frame period. As a result, the value of the luminance signal ateach detection point can be acquired.

A flow of decision concerning the pattern portions in the I/F unit 155will now be described with reference to FIG. 33. A decision is madewhether a vertical pulse has been received (S3301). Unless received, theI/F unit 155 waits for reception of a vertical pulse. If received, theI/F unit 155 proceeds to S3302. The I/F unit 155 acquires the value ofthe luminance signal Y at each detection point from the pattern portiondetector 1511 (S3302) and finds a difference from the preceding frame ateach detection point (S3303).

With respect to the detection points P11, P12 and P13 in the patternportion display region when the 4:3 video image is displayed, a decisionis made whether the difference (ΔP11, ΔP12, ΔP13) from the precedingframe is “0” (S3304). When this difference is not “0”, the I/F unit 155judges that a pattern portion is not contained and proceeds to S3308.

On the other hand, if the difference is “0”, the I/F unit 155 judgesthat there is a possibility that a pattern portion will be contained,and proceeds to S3305. Even if the difference at P11, P12 and P13 is“0”, there is a possibility that the contents will have a motion only inthe central part. With respect to the detection points P21, P22 and P23in the contents display region when the 4:3 video image is displayed, adecision is made whether the difference (ΔP21, ΔP22, ΔP23) from thepreceding frame is “0” in order to discriminate such contents at S3305.When this difference is “0”, the I/F unit 155 judges that the contentshave a motion only in the central part, and proceeds to S3308.

When the frame difference at P21, P22 and P23 is not “0”, the I/F unit155 judges that a pattern portion is contained, and sets a flag providedin a part of a register to indicate whether there is a pattern portionto “1” (there is a pattern portion) (S3306). And the I/F unit 155 issuesan interrupt to the CPU 7, requests register reading, and notifies theCPU 7 that the contents have a pattern portion (S3307). At S3308, thevalue of the luminance signal Y at each detection point is stored aspreceding frame data.

FIG. 34 shows a processing flow in the CPU 7. Correction characteristicsupdate processing in the CPU 7 is executed by receiving the interrupt141 from the I/F unit 155. When the pattern flag is “0” at S3401, i.e.,when there is no pattern portion, the CPU 7 calculates correction datato conduct the picture quality enhancement processing by using themethod described in the first embodiment or the second embodiment atS3402, and transmits the correction data to the I/F unit 153 (S3404).When the pattern flag is “1” at S3401, i.e., when there is a patternportion, the CPU 7 sets correction data=“0” at S3403, and transmits thecorrection data to the I/F unit 153 (S3404).

A concrete example of pattern portion detection in the I/F unit 155 willnow be described with reference to FIGS. 35A-35C and 36A-36C.

FIGS. 35A to 35C show an example of the case where contents having nopattern portions are input. FIG. 35A shows a video image of a precedingframe. FIG. 35B shows a video image of the next frame. FIG. 35C showsvalues of the luminance signal Y in the preceding frame and thesubsequent frame at each detection point and their differences.

It is supposed in FIG. 35A that, for example, the value of the luminancesignal Y in the video signal is 100 at sun 351, 80 at sky 352, 50 at alarge mountain 353, and 40 at a small mountain. As for the value of theluminance signal Y in the preceding frame at each detection point,P11:100, P12:80, P13:50, P21:80, P22:50 and P23:40 are retained asindicated in a column of frame 1 in FIG. 35C.

If a video signal as represented by FIG. 35B is input, the I/F unit 155acquires the value of the luminance signal Y at each detection pointshown in FIG. 35B after detection of the vertical pulse, according tothe flow shown in FIG. 33. For example, P11:80, P12:80, P13:80, P21:100,P22:80 and P23:50 are acquired as indicated in a column of frame 2 inFIG. 35C. At S3303, the I/F unit 155 calculates a difference between theframe 1 and the frame 2. As a result, ΔP11:−20, ΔP12:0, ΔP13:30,ΔP21:20, ΔP22:30 and ΔP23:10 are obtained as indicated in a column offrame difference in FIG. 35C. Since ΔP11 and ΔP13 are not “0” at S3304,the I/F unit 155 proceeds to S3308, stores the Y values at respectivedetection points as values of the preceding frames, and finishes theprocessing. Therefore, it is not judged that there is a pattern portion.

FIGS. 36A to 36C show an example of the case where contents havingpattern portions are input. FIG. 36A shows a video image of a precedingframe. As shown in FIG. 36A, pattern portions are inserted on the leftand right of 4:3 contents. If such a video signal is input, P11:23,P12:22, P13:25, P21:100, P22:50 and P23:40 are retained as the values ofthe luminance signal Y in the preceding frame as indicated in a columnof frame 1 in FIG. 36C.

The I/F unit 155 acquires the value of the luminance signal Y at eachdetection point shown in FIG. 36B according to the flow shown in FIG.33. Results of the acquisition become, for example, P11:23, P12:22,P13:25, P21:80, P22:80 and P23:50 as indicated in a column of frame 2 inFIG. 36C (S3302). The difference between the frame 1 and the frame 2becomes ΔP11:0, ΔP12:0, ΔP13:0, ΔP21:-10, ΔP22:30 and ΔP23:10 as shownin FIG. 36C (S3303). Since ΔP11, ΔP12 and ΔP13 are “0” at S3304, the I/Funit 155 proceeds to S3305, where a decision is made whether ΔP21, ΔP22and ΔP23 are “0”. In the present example, ΔP21, ΔP22 and ΔP23 are not“0”. Therefore, the I/F unit 155 proceeds to S3306, and sets the patternportion flag=“1” in the register. At S3307, the I/F unit 155 issues aninterrupt to the CPU 7, requests register reading, and notifies the CPU7 that the contents have pattern portions. At S3308, the I/F unit 155stores the values of the luminance signal Y at respective detectionpoints, and finishes the processing.

The CPU 7 recognizes that the contents have pattern portions bydetecting the pattern portion flag=“1”, and writes correctioncharacteristics which output the input signal as it is, into the I/Funit 155. As a result, the picture quality enhancement processing at thetime of display of contents having pattern portions is stopped.

As heretofore described, it is detected whether the video signalincludes a pattern portion. If a pattern portion is contained, thepicture quality enhancement processing for the video signal is stopped.As a result, flicker caused in the pattern portions by a change inluminance and color is prevented, and it can be made easy to view thecontents.

In the present embodiment, the case where the picture qualityenhancement processing is stopped in response to the detection ofpattern portions has been described. However, this is not restrictive.Update of the correction data may be stopped in response to thedetection of the pattern portion. By stopping the update of thecorrection data, it is possible to prevent the luminance and color ofthe pattern portions from being changed.

The example in which the image having pattern portions is judged byusing the difference in the luminance signal Y between two consecutiveframes has been described. However, this is not restrictive.Alternatively, at least three consecutive frames may also be used. Or adecision may be made by using frames thinned at definite intervals andextracted.

Fourth Embodiment

If the pattern portions are formed of single color of black, correctioncauses a less change in the pattern portions as compared with the casewhere the pattern portions are formed of patterns or a single chromaticcolor. When it is detected that pattern portions have been added to theleft and right of contents, it is detected in the present embodimentwhether the pattern portions are black no-picture areas. If the patternportions are black no-picture areas, then the video signal is corrected.This case will now be described. By the way, in the present embodiment,a portion that is contained in the pattern portions and that is not ablack no-picture area portion is used as a wallpaper area portion.

FIG. 37 is a block diagram showing another configuration example of thepicture quality enhancement circuit in the portable telephone. Thepicture quality enhancement circuit differs from the picture qualityenhancement circuit shown in FIG. 27 that a characteristic pointdetection area controller 1512 is provided.

FIG. 38 shows a configuration example of the characteristic pointdetection area controller 1512. A horizontal area detection counter15121 counts dot clock pulses in an input video signal. When the counthas reached a predetermined value, the horizontal area detection counter15121 outputs a horizontal enable signal. When the count has coincidedwith the number of pixels in the horizontal direction of the displaydevice 16, the horizontal area detection counter 15121 outputs ahorizontal pulse and clears the count. A vertical area detection counter15122 counts the horizontal pulses output from the horizontal areadetection counter 15121. When the count has reached a predeterminedvalue, the vertical area detection counter 15122 outputs a verticalenable signal. When the count has coincided with the number of pixels inthe vertical direction of the display device 16, the vertical areadetection counter 15122 outputs a vertical pulse and clears the count.

An AND gate 15123 outputs a logical product of the horizontal enablesignal output from the horizontal area detection counter 15121 and thevertical enable signal output from the vertical area detection counter15122. An OR gate 15124 outputs a logical sum of a detection mask signalinput from the I/F unit 155 and the output of the AND gate 15123 to thecharacteristic point detector 154 as a characteristic point detectionenable signal. The characteristic point detector 154 handles only thevideo signal obtained while the characteristic point detection enablesignal is at the high level as the subject of histogram computation andaverage value calculation, and disregards the video signal obtainedwhile the characteristic point detection enable signal is at the lowlevel. As a result, it becomes possible to conduct the characteristicpoint detection only in the contents display area with the blackno-picture area excluded.

An example of operation of the characteristic point detection area 1512controller will now be described with reference to FIGS. 39 to 42E.

FIG. 39 shows positions and sizes of black no-picture areas on thedisplay device 16. As for the number of pixels on the display device 16,it is supposed that, for example, there are 320 dots in the horizontaldirection and 180 dots in the vertical direction in the same way as theabove-described embodiments. It is also supposed that the aspect ratiois 16:9. In the present example, the black no-picture areas extend over40 dots on the left and right of the display device 16.

An example of operation in the horizontal area detection counter 15121will now be described with reference to FIGS. 40A-40C. In the horizontalarea detection counter 15121, 40 and 280 which are x coordinates of astart point and an end point of a horizontal detection area enablesignal are preset, and 320 which is the number of pixels in thehorizontal direction of the display device 16 is preset in order togenerate the horizontal pulse. As for the presetting method, it may beset from the CPU 7, or the preset values may be fixed within thehorizontal area detection counter 15121. The initial values are thuspreset in the horizontal area detection counter 15121. As a result, thehorizontal area detection counter 15121 counts dot clock pulses inputthereto. When 40 clock pulses are counted, the horizontal detection areaenable signal is changed to the high level. When 280 clock pulses arecounted, the horizontal detection area enable signal is changed to thelow level. In addition, when 320 clock pulses are counted, a high-levelhorizontal pulse is output. When the horizontal area detection counter15121 has output the horizontal pulse, it resets the count, resumescounting from “0”, and repeats the operation of periodically outputtingthe horizontal detection area enable signal and the horizontal pulseoutput at the above-described timing.

An example of operation in the vertical area detection counter 15122will now be described with reference to FIGS. 41A-41C. In the verticalarea detection counter 15122, 1 and 320 which are x coordinates of astart point and an end point of a vertical detection area enable signalare preset, and 320 which is the number of pixels in the horizontaldirection of the display device 16 are preset in order to generate thevertical pulse. As for the presetting method, it may be set from the CPU7, or the preset values may be fixed within the vertical area detectioncounter 15122. The initial values are thus preset in the vertical areadetection counter 15122. As a result, the vertical area detectioncounter 15122 counts horizontal pulses input thereto. When one clockpulse is counted, the vertical detection area enable signal is changedto the high level. When 320 clock pulses are counted, i.e., at alltimes, the high level is output as the vertical detection area enablesignal. In addition, when 180 clock pulses are counted, a high-levelvertical pulse is output. Upon outputting the vertical pulse, thevertical area detection counter 15122 resets the count, resumes countingfrom “0”, and repeats the operation of periodically outputting thevertical detection area enable signal and the vertical pulse output atthe above-described timing. Here, the example of the case where a videosignal having black no-picture areas inserted only on the left and rightof the contents display area as shown in FIG. 39 is input will bedescribed. However, this is not restrictive, but the black no-pictureareas may be inserted above and below the contents display area. In thatcase, the CPU 7 should set the start position and the end position ofthe contents display area in the vertical direction.

Input and output waveforms of the AND gate 15123 are shown in FIGS.42A-42E. Only when both the horizontal detection area enable signal andthe vertical detection area enable signal are at the high level, the ANDgate 15123 outputs the high level. Therefore, the high level is outputover a period ranging from the 40th dot clock pulse to the 280th clockpulse in the horizontal direction and over a period ranging from thefirst dot clock pulse to the 180th dot clock pulse in the verticaldirection, i.e., while the video signal corresponding to the contentsdisplay area is flowing.

An OR gate 15124 outputs a logical sum of the output of the AND gate15123 and the area detection mask signal input from the I/F unit 155 tothe characteristic point detector 154 as a sampling enable signal. Byusing this OR gate 15124, it is possible to control whether to conveythe output of the AND gate 15123 supplied from the CPU 7 via the I/Funit 155 to the characteristic point detector 154 as it is or fix theoutput of the OR gate 15124 to the high level to mask the output of theAND gate 15123. As a result, the CPU 7 can control whether to conductthe characteristic point detection in the whole screen including theblack no-picture area or conduct the characteristic point detection onlyin the contents display area which does not include the black no-picturearea. Here, the example of the latter case will be described. If thearea of the black no-picture area is small, however, there is not aserious problem even if the former case is used.

A flow of decision concerning the black no-picture area in the I/F unit155 will now be described with reference to FIG. 43. A decision is madeat S4301 whether a vertical pulse has been received. If received, theI/F unit 155 acquires the value of the luminance signal Y at eachdetection point from the pattern portion detector 1511 (S4302). AtS4303, the I/F unit 155 finds a difference from the preceding frame ateach detection point. With respect to the detection points P11, P12 andP13, which are included in the pattern portion when the 4:3 video imageis displayed, a decision is made at S4304 whether the difference (ΔP11,ΔP12, Δ13) from the preceding frame is “0”. When this difference is not“0”, the I/F unit 155 judges that a pattern portion is not contained andproceeds to S4310.

On the other hand, if the difference is “0”, the I/F unit 155 proceedsto S4305. With respect to the detection points P21, P22 and P23, whichare included in the contents display region when the 4:3 video image isdisplayed, a decision is made at S4305 whether the difference (ΔP21,ΔP22, ΔP23) from the preceding frame is “0”. When this difference is“0”, the I/F unit 155 judges that the points are not in the patternportion, and proceeds to S4310.

When the frame difference at P21, P22 and P23 is not “0”, the I/F unit155 judges that the points are included in a pattern portion, and makesa decision at S4306 whether the pattern portion is a black no-picturearea portion. When the value of the luminance signal Y at P11, P12 andP13 is not “0”, the I/F unit 155 judges the pattern portion to be awallpaper portion and sets a flag provided in a part of the register toindicate whether a wallpaper portion is present to “1”: “a wallpaperportion is present” (S4307). If the value of the luminance signal Y is“0”, the I/F unit 155 judges the pattern portion to be a blackno-picture area, and sets a flag provided to indicate whether ano-picture area is present to “1”: “a no-picture area is present”(S4308).

At S4309, the I/F unit 155 issues an interrupt to the CPU 7, requestsregister reading, and notifies the CPU 7 that the contents have awallpaper portion or a no-picture area. At S4310, the value of theluminance signal Y at each detection point is stored as preceding framedata.

FIG. 44 shows a processing flow in the CPU 7. Correction characteristicsupdate processing in the CPU 7 is executed by receiving the interrupt141 from the I/F unit 155. When the wallpaper flag is “1” at S4401,i.e., if a black no-picture area portion is contained in the patternportion, then the CPU 7 sets correction data=“0” at S4403 and proceedsto S4406. On the other hand, if the wallpaper flag is “0”, the CPU 7proceeds to S4402.

When the no-picture flag is “1” at S4402, i.e., if a no-picture areahaving a single black color is contained, the CPU 7 fixes the output forthe input gradation that is a definite value or less to “0”, calculatescorrection data to conduct picture quality enhancement processingsuitable for contents having a non-picture area, and determines acharacteristic point detection area (S4405). By the way, the picturequality enhancement processing suitable for contents having anon-picture area will be described later.

If the no-picture flag is “0” at S4402, then the CPU 7 calculates thecorrection data to conduct ordinary picture quality enhancementprocessing (S4404). At S4406, the CPU 7 transfers the correction data tothe I/F unit 153.

Hereafter, an operation example in the case where contents having blackno-picture area portions shown in FIGS. 45A-45C are input will bedescribed. FIG. 45A shows a video image of a preceding frame. As shownin FIG. 45A, no-picture area portions are inserted on the left and rightof 4:3 contents. If such a video signal is input, P11:0, P12:0, P13:0,P21:100, P22:50 and P23:40 are retained as the values of the luminancesignal Y in the preceding frame as indicated in a column of frame 1 inFIG. 45C. In the flow diagram shown in FIG. 43, the vertical pulse isdetected at S4301. Thereafter, the I/F unit 155 acquires P11:0, P12:0,P13:0, P21:80, P22:80 and P23:50 as the value of the luminance signal Yat each detection point shown in FIG. 45B as indicated in a column offrame 2 in FIG. 45C, and the I/F unit 155 proceeds to S4303. At S4303,the difference between the frame 1 and the frame 2 is calculated.Therefore, the difference between the frame 1 and the frame 2 becomesΔP11:0, ΔP12:0, ΔP13:0, ΔP21:-10, ΔP22:30 and ΔP23:10 as indicated in acolumn of the frame difference in FIG. 45C. Since AP11, AP12 and AP13are “0” at S4304, the I/F unit 155 proceeds to S4305, where a decisionis made whether ΔP21, ΔP22 and ΔP23 are “0”. Since ΔP21, ΔP22 and ΔP23are not “0”, the I/F unit 155 proceeds to S4306.

Since P11, P12 and P13 are “0” at S4306, the I/F unit 155 proceeds toS4308. At S4308, the I/F unit 155 sets no-picture flag=“1” in theregister and proceeds to S4309. At S4309, the I/F unit 155 issues aninterrupt to the CPU 7, requests register reading, notifies the CPU 7that the contents have no-picture area portions, and proceeds to S4310.At S4310, the I/F unit 155 stores the values of the luminance signal Yat respective detection points, and finishes the processing. Even if thecontents have the input gradation in the range of 0 to 15, correction isconducted at S4405 so as to fix the output for the input signal in therange of 0 to 15 to 0 as shown in FIG. 46, as the correctioncharacteristics suitable for the contents having no-picture areaportions. As a result of such correction, a part of the gradation on theblack side is lost. However, there is a merit that the noise containedin the no-picture area portions is removed and the patterns portions canbe displayed as uniform black. It is possible to make the image lookmore attractive.

In order to remove the influence of the black no-picture area portionupon the characteristic point calculation of the image, the CPU 7specifies coordinates of the contents display area, sets a desired countin each of the horizontal position counter 15111 and the verticalposition counter 15112, and presets a value output to the I/F unit 153so as to output the low level to the OR gate 15124. By setting thepreset value into the I/F unit 153 at S4406, it is possible to conductpicture quality correction optimum for the contents having no-picturearea portions.

In the present embodiment, the case where the video signal is correctedwhen contents having black no-picture area portions are input has beendescribed. However, this is not restrictive, but correction may beconducted when white no-picture area portions are contained. In thiscase, a decision is made at S4306 in FIG. 43 whether P11 and so on are255. Even if noise is contained, flicker in the pattern portion can beprevented by exercising control so as to fix the gradation on the whiteside assuming at least a definite value to “255”.

In FIG. 37, the characteristic point detection area controller 1512 isprovided only on the characteristic point detector 154 side. However, itis also possible to control the modulation area as well by providing thecharacteristic point detection area controller 1512 on the modulator 152side as well. As a result, for example, it is possible to exclude thepattern portions and conduct correction only in the contents displayarea. Even in a pattern portion that is not a black or white no-picturearea but that has, for example, a pattern, the output may be made “0” todisplay a single black color if every gradation level distributes in arange below a certain definite level. On the contrary, if everygradation level distributes in a range above a certain definite level,the output may be made “255” to display a single white color.

In the foregoing embodiments, the case where pattern portions are addedon the left and right of the image has been described as an example.However, this is not restrictive, but the embodiments may be applied tothe case where pattern portions are contained above and below the image.Detection of the pattern portions located above and below the image canbe coped with a similar processing method by disposing the detectionpoints above and below the image.

In addition, time is displayed on the screen or a caption or a mark isinserted on the periphery of the screen, in some cases. In order to copewith such a case, it is also possible to previously exclude definiteportions located above and below the image and located on the left andright of the image from the characteristic point detection area andconduct the characteristic point detection only in the central part ofthe screen, regardless of the result of the decision in the patternportion detector 1511. As a result, it is possible to suppress changesin characteristic data caused by insertion of the caption or the likeand prevent flicker and color changes on the screen.

The foregoing invention has been described in terms of preferredembodiments. However, those skilled, in the art will recognize that manyvariations of such embodiments exist. Such variations are intended to bewithin the scope of the present invention and the appended claims.

1. A video processing apparatus comprising: an input unit to which avideo signal containing contents is input; a detector which detectswhether pattern portions other than contents are contained in the videosignal input to the input unit; a corrector which corrects the videosignal input to the input unit; and a controller which controls thecorrector to cause the corrector to correct the video signal input tothe input unit when the pattern portions are not contained, and whichcontrols the corrector to cause the corrector not to correct the videosignal when the pattern portions are contained.
 2. The video processingapparatus according to claim 1, comprising: a characteristic pointdetector which detects a level or distribution of at least one ofluminance, hue and saturation of the video signal, wherein the correctorcorrects the video signal according to the level or distributiondetected by the characteristic point detector.
 3. A video processingapparatus comprising: an input unit to which a video signal containingcontents is input; a detector which detects whether pattern portionsother than contents are contained in the video signal input to the inputunit; a characteristic point detector which detects a level ordistribution of at least one of luminance, hue and saturation of thevideo signal input to the input unit; a corrector which changescorrection characteristics according to a result of detection outputfrom the characteristic point detector, and corrects the video signalinput to the input unit; and a controller which controls the correctorto cause the corrector not to change the correction characteristics inthe corrector when the pattern portions are contained.
 4. The videoprocessing apparatus according to claim 1, wherein the pattern portionsare wallpaper areas or no-picture areas having a single color added toleft and right of the contents or above and below the contents anddisplayed.
 5. A video processing apparatus comprising: an input unit towhich a video signal containing contents is input; a pattern portiondetector which detects whether a pattern portion other than contents iscontained in the video signal input to the input unit; a no-picture areadetector which detects whether the pattern portions are no-picture areashaving a single color; a corrector which corrects the video signal inputto the input unit; and a controller which controls the corrector tocause the corrector to correct the video signal input to the input unitwhen the pattern portions are not contained and when the patternportions are the no-picture areas, and which controls the corrector tocause the corrector not to correct the video signal when the patternportions are not the no-picture areas.
 6. The video processing apparatusaccording to claim 5, comprising: a characteristic point detector whichdetects a level or distribution of at least one of luminance, hue andsaturation of the video signal, wherein when the no-picture areadetector has detected that the pattern portions are no-picture areas,the characteristic point detector detects a level or distribution of atleast one of luminance, hue and saturation of the video signal otherthan the no-picture areas.
 7. The video processing apparatus accordingto claim 5, wherein the pattern portions are portions added to left andright of the contents or above and below the contents and displayed. 8.The video processing apparatus according to claim 5, wherein theno-picture areas have a black color or a white color.